The development of sandals with one-piece molded bottoms date back in history to the use of wooden clogs, which were originally made without separate outsoles. The term "outsole" has been defined as the bottom sole thickness comprising the surface which is exposed to wear. By contrast, the conventional shoe includes an "insole" which is defined as the piece of leather or other material between the sole and the foot on to which the upper part of the shoe is connected. Within the past ten or fifteen years, as petro chemicals and other plastics have been developed for the footwear industry, the one-piece molded bottom has become common. Such one-piece molded bottom eliminates the need for separate outsoles and heels and may eliminate the need for insoles used in the conventional shoe. Also, the use of the one-piece molded bottom eliminates the requirement in some instances for steel shank requirements located under the arch.
While the above noted advantages, as well as others not mentioned, are derived from the use of the one-piece molded bottom sandal, there are certain disadvantages common to the use of such sandal. One problem arises due to the anatomical and functional differences between the inside and outside longitudinal arch areas of the normal foot, which differences cause the natural tendency of the ankle to tip toward the inside of the foot, resulting in pronation.
There are various types of insoles and inserts that have been proposed for reducing foot stresses and fatigue and for supporting parts of the feet including the arch.
In U.S. Pat. No. 2,788,591 to Gibson, there is described a sandal for supporting the arch of the foot in which a flexible strap secured to the middle portion of the sole structure provides an arch support as well as securing the sandal to the foot. The flexible strap is designed to loop around the instep of the wearer's foot, then extend around under the arch of the foot and through a slot in the flexible flap. Such straps by their very design around and under the wearer's arch would be extremely uncomfortable in actual use.
U.S. Pat. No. 4,084,333 to Del Vecchio is described as an innersole for footwear and includes a molded plastic insole shaped to the foot of the wearer. The innersole provides at its upper part, at the heel, a depression into which the foot heel portion is received and held and allows the arch of the sole to rest and adhere against the innersole. Here, the inside and outside lateral upturned walls are approximately the same height and do not allow for the physical and functional differences between the inside longitudinal arch and the commonly referred to "outer arch" at the outside edge of the foot in the area of the fifth metatarsal bone.
Also, footwear insoles are designed for insertion between the sole of a shoe and the foot. One example of an insole or insert designed for supporting the foot to relieve stresses and pressures on certain portions of the foot which cause corns, callouses and other deformities is disclosed in U.S. Pat. No. 2,008,207 to Greenberg. Here, a foot support is designed as an insole or an insert for conventionally constructed closed shoes. The design and manufacture of closed shoes, including the lasts, bottom patterns, shoe uppers, and construction techniques, are acknowledged to be different from those customarily used in open shoes and sandals. For example, inserts cannot be used in sandals. The patentee states that the insole with high inside portions tends to throw excessive weight on the fifth or little toe at the outside of the foot. To overcome this problem, the patentee provides an elevated outside portion on the insert near such little toe to support the anterior transverse arch near such little toe. The design of insoles and inserts for closed shoes does not solve the problems inherent in sandals and the one-piece molded bottom, namely the tipping of the ankle toward the inside of the foot, causing pronation, and the securing of the foot to the molded bottom is a stabilizing fit.
U.S. Pat. No. 4,020,569 to Fukuoka relates to a sole including an outersole, an insole and a heel section of a footwear such as a shoe or a sandal. A reinforcing plate also serves as an insole which is mounted on the rear half of the sole body. The reinforcing plate represents the art and complex structure involved in designing a rigid or semi-rigid reinforcing means into the rear half of a sole body to reduce foot fatigue.
It is an object of the present invention to provide a sandal which discourages or prevents tipping of the ankle toward the inside of the foot thus preventing pronation. It is another object to provide a sandal which promotes ankle stability. It is another object to provide a sandal of the one-piece molded bottom type which is designed to accommodate the anatomical and functional differences between the inside and outside longitudinal arch areas of the normal foot. It is a further object to provide a sandal which is both functional and comfortable and assures both proper positioning of the foot on the molded bottom as well as a stabilizing fit thereon.
It is to be understood that as used herein, the terms "stabilizing wall" and "stabilizing flange" are used interchangeably.